Can Zotero's layout be changed?
Why is the core information (the actual record with the bibliographic data) in the Zotero layout placed in the side bar, literally shiffted aside? (While the list that is only used for searching is central in the screen, covering much of the screen, which distracts very much from the information one is working with.) Technically Zotero works fine, but the layout is not functional. Can this layout be changed?
Upgrade Storage
Stacked view (under View --> Layout) might work better for you, and, of course, you can resize the different panes using hold&drag.
It's not a "sidebar". It's the item details pane. This is a standard hierarchical three-pane layout, used by innumerable programs for decades, with folders/collections on the left, a list view in the middle, and details on the right.
You can use Stacked mode (View → Layout → Stacked View) if you prefer the details at the bottom.
"Zotero" unless otherwise specified always refers to the Desktop app, which is more customizable & more powerful.